Ceramic glaze



in a decorative glaze.

complete description and claims.

CERAMIC GLAZE Robert W. Foraker, Westfield, N.J., assignor to NationalLead Company, New York, N.Y., a corporation of New Jersey No Drawing.Application September 5,1957 Serial No. 682,085

Claimsfl (Cl. 106-54) This invention relates to a ceramic glaze. Morespecifically, this invention relates to a white-opacifiedceramic glaze,opacified and whitened with TiO In particular, this invention relatesespecially to a self-opacified-titaniacontaining glaze of the alkaliboroalumino-silicate type.

This application is a continuation-in-part of my application Serial No.500,697, filed April 11, 1955, now

the firedpiece resulting in spalling, cracking, chipping or crazing.Aside from the necessary limitations on the coefiicient' of expansion,other properties are desirable Among'these may be mentioned highopacity, gloss, durabilityat a low'maturingtemperature, and purity ofcolor. Particularly in the case of .a white glaze, a pure white color isto be desired.- Such a base color lends itself readily to theproduction, if dedesired, of pastel shades by the addition of minoramounts of tinting'agents to the formulation.

Ceramic glazes'designed to provide the above desirable properties andovercome the disadvantages of the prior art have been described in'co-pending application Serial No. 381,959, filed September 23, 1953, nowabandoned, and assigned to the assignee hereof. These glazes, however,while successful in achieving the objects for which they were ,designed,suffered from certain disadvantages. In particular, it was found that arelatively high proportion of A1 0 was required in the formulation topromote-optimum crystallization of -the-- titania and-thereby give goodopacification. This high proportion of A1 0 however, resulted inrelatively high melting point compositions sothat the frit batches couldnot be smelted with out resorting to higher temperatures than might bedesired for many applications.

nited States Patent- O It is, therefore, an object of the presentinvention to provide an improved ceramic frit composition capable offorming a glaze upon firing. It is a further object to provide a ceramicglaze having a coefficient of expansion similar to ceramic wall tile.Still another object is to provide a durable, white opaque ceramic glazehaving a relatively low maturing temperature. An additional object is toprovide a frit composition which may be smelted at a relatively lowtemperature to produce a frit capable of being fired to provide adurable, white opaque glaze of the recrystallizing type. Otherobjectsand advantages will become apparent from the following moreBroadly, this invention contemplates a ceramic frit composition capableofforming a glaze upon firing, comprising Si0 in amount from to 70%, B 0in amount from 7 to 15 A1303 in amount from 1 to 5%, TiO in amount from7 to 15%, ZrO in amount from 0 to --3%, an alkali selected'from thegroup consisting of K 0 and Na O in amount from 10% to 15%, and MgO inamount froinO to 5 the sum of-the A1 0 ZrO and 2,929,?28 Patented Mar.22, 1960 MgO being from 3 to 10%, all of the above percentages beingmole percentages.

ZnO may also be added to the above glaze composition in amount of aboutone mole percent. The addition of ZnO tends to improve the gloss of theresultant glaze and produces a somewhat smoother surface.

In a particularly desirable embodiment this invention contemplates aglaze of the above type which further comprises from 1 to 3% P 0 Inanother particularly desirable embodiment this invention contemplates aglaze of the above type which further comprises from 1 to 5% F To insurethat thefrit composition will smelt at a relatively low temperature, itis important that the Al O be no higher than about 5%. As disclosed inthe above-mentioned co-pending application, such low proportions of A1 0would ordinarily be expected to result in poor crystallization of theTi0 during the final firing operation, with consequent loss of whitenessand opacification. It has been found, however, that a sufficient degreeof whitness and opacity is achieved even using relatively lowpercentages of A1 0 providing the sum of the Al O ,'the ZrO and MgO (ifpresent) is kept within the range 3 to 10%. As'stated above, theopacifier is TiO and should be presentin amount from 7 to 15 .molepercent. p a Throughout the above discussion and elsewhere herein,except as otherwise stated, the percentagesdiscussedare mole percentagesbased on the sum of the oxides present.

. .Afcerami gla having. a comp si ion. as. just describe may be appliedto wall tile and other common clay ceramic-materials such as whitewarebodies, terra cotta,

earthenware and structural clay bodies which mature at temperatures intheneighborhood of 15007111 .to.2000 F. to produce a highly opaque whiteglaze. The glaze is of the recrystallizing type, by. whichfis'm'eantthat it 1 tion and application of ceramic glazes according to thisinvention, the following examples are presented:

Example 1 A frit batch was prepared by mixing the following ingredients:

Parts by weight 140.9 39.6

A1203 M 2 03 NaNO 27.2

TiO 48.0

After thorough mixing the mixture was smelted for Ila-hours at 2400" F.and quenched in water. A clear frit was produced which had the followingoxide composition:

Mole

Percent weaves One hundred parts of the frit were mixed with 28.4 partsof china clay, 0.25 part of KCl, 0.25 part of NaAlO and 55 parts ofwater. The mixture was made into a slip by grinding in a ball mill andscreening through an 80 mesh screen to remove the coarse particles.

The slip was then sprayed onto anarchitcctural' tile at the dry weightof 30 grams per square foot and the tile containing the sprayed slip wasdried and then heated at 250 F. per hour to 2000 F. and held for 30minutes to mature the glaze on the tile. The matured glaze was allowedto cool to room temperature over a period of 16 hours. The resultingglazedtile exhibited a white color with good surface texture and with nodetectable tendency to craze, chip or 'sp all.

glaze was white with a slight yellow undertone and showed excellentgloss, texture and acid resistance, with good opacity and no discernibletendency to craze or spall. Example 3 The procedure of Example 1 wasagain repeated, substituting the following batch composition:

Parts by Weight The batch was mixed and smelt'ed at 2350 F. for onehour. but still sufficientlyfiuid to be handled and poured without unduedifilculty or losses. The melt was quenched as above described .toproduce a frit having the following o'xide composition: 1

The melt was fairly viscous at this temperature,

Mole

Weight Percent Percent This frit was ball-milled, screened and appliedto a tile body by the same procedure used in Example 1 and Thisparticular exampl'e'represents thebest method for then heated at a rateof R per'h'our to 17000 and Preparmg the glaze of the mstant 7 held for1 hour, and allowed to cool in the kiln overl 2 night. The resultingglaze was similar in color to-that 8 described in Example 2. and wasalso of good quality Another batch was prepared using th'e following in"with respect to gloss, texture, acid and alkali resistance, gredients:1 and freedom from crazing and cracking.

' Parts 'by weight 1 E l 4 SiO 14 0 xamp e I 'Na B O 51,6 A frit batchwas prepared bymixing the following in 2 3 9.8 95 gredients: Na,,C0 13.8Parts by weight ZrO -SiO f 14.6 102 149p 7 2 2 M 1340, 38.7 The batchwas thoroughly mixed and snielted for-one 3 hour at 2350" F. andquenched in water "to produce a 30 A1203 i I frit having the followingoxide composition. M C p 1 5.0 T I I a TiOg 1 31.0 M919. W v g 4 ifi fif??? The hatchfwas mixed well and s'melted for one hour 1 at 23503? andquenchedin water. A clear frit Z;, f 7 31? 21-3 producedwhich had thefollowing oxide composition: A1203 2.4 3.7 I 2-: .0 I Tioi" "8.5 V 10.4ggfggg 100.0 100.0

siol 01. 8 57. 0 1319:. 9.6 10.3 A1103" 5.1 8.0 .*The quenched fritwasthen ball-milled with the same g zge 3-3 mill additions andin thesame manner as that described o ,1I 0 12 in Example 1, applied to asimilar tile body at the same T401" 9'5 1 weight and heated at300-.F./.hr. to a temperature of I 1000 100.0 1700 F. and held .at 1700ffor one-hourand then. a w i permitted to cool to room temperature. Theresulting The fi'it was then milled, screened and sprayed "onto 3{tileb'oilie in the same manner as 'that described in Ex- Example 5'.The procedure of Example '1 was again repeated sub- -stitu ting thefollowing batch composition:

1 Parts by weight H The batch was mixed well smelted for one hour MoleWeight Percent Percent $100 00.0 55.9 $1203.- 9.3 10.1 A1203 5.0 7.9N820 11.1 10.7 MgO 1.5 0.9 ZnO 1.0 1.3 F9 2.8 1.7 T101. 9.3 11.5

The frit was then made into a slip using the same procedure as thatdescribed in Example 1. The slip was sprayed at the same Weight on tilebodies and the temperature was raised at the rate of 250 F. per hour tothe maturing temperature of 1700 C. for one-half hour. The resultingglaze had an excellent color and texture with good opacity and notendency to craze or spall.

Example 6 A frit batch was prepared according to the procedure ofExample 1 except the following ingredients were employed:

Parts by weight Si 146.2 N32B407 Na CO NaNO 20.4 A1 0 11.8 ZrO +SiO MgCO5.0 ZnO 3.2 TiO 24.7

The batch after being thoroughly mixed was smelted for one hour at 2350F. and then quenched in water. The frit produced had the following oxidecomposition:

Mole Weight Percent Percent $10 63.2 58.1 B203 9. 8 10. 5 A1 03 2.9 4.5Na O 11.0 11.0 MgO 1.5 0.9 ZrO2.- 2.3 4.3 ZnO 1.0 1.3 T10, 7.7 9.4

A slip was prepared from the frit using the procedure described inExample E and the slip was sprayed at the same weight on three tilebodies and the temperature was raised at the rate of 325 F. per hour tothe maturing temperature. The three pieces were matured respectively at1600 F., 1700 F. and 1800 F. for A2 hour. All of these possessed a goodcolor and texture and possessed no detectable tendency to craze orspall.

Example 7 Another frit batch was prepared according to the procedure ofExample 1 except the following ingredients were employed:

Parts by weight SiO 148.0 Na B O A1 0 11.4 NH H PO 13.8 Na CO 25.7 ZrO-SiO 16.9 Ti0 31.0

The batch was thoroughly mixed and smelted for one hour at 2350" F. andquenched in water. The frit pro duced had the following oxide analysis;

Mole Weight Percent Percent SiOL 62.8 56.4 21%;-

A slip was prepared from the frit using the procedure described inExample 1 and the slip was sprayed at the same weight on three tilebodies and the temperature was raised at the rate of 325 F. per hour tothe maturing temperature. The three pieces were matured respectively at1600 E, 1700 F. and 1800 F. for /2 hour. All of these possessed a goodcolor and texture and possessed no detectable tendency to craze orspall.

From the above description and by the examples shown, ceramic glazespossessing relatively low smelting and maturing temperatures have beenproduced using small proportions of aluminum oxide. The ceramic glazesproduced by the instant invention have low coeflicients of expansion andsatisfactory viscosity characteristics at relatively low maturingtemperatures.

The ceramic glazes of the instant invention are durable and possess goodcolor and surface texture.

While this invention has been described and illustrated by the examplesshown, it is not intended to be strictly limited thereto, and othervariations and modifications may be employed within the scope of thefollowing claims.

I claim:

1. A frit composition of the self-opacifying alkali boroaluminosilicatetype consisting essentially of SiO in amount from about 55 to about 70mole percent, B 0 in amount from about 7 to about 15 mole percent, Al Oin amount from about 1 to about 5 mole percent, TiO in amount from about7 to about 15 mole percent, ZrO in amount from 0 to about 3 molepercent, an alkali metal oxide selected from the group consisting of K 0and Na O in amount from about 10 to about 15 mole percent, and MgO inamount from 0 to about 5 mole percent, the sum of the N 0 ZrO and MgObeing from about 3 to about 10 mole percent.

2. An opacified glaze composition of the self-opacitying type consistingessentially of SiO in amount from about 55 to about 70 mole percent, B 0in amount from about 7 to about 15 mole percent, A1 0 in amount fromabout 1 to about 5 mole percent, TiO in amount from about 7 to about 15mole percent, ZrO in amount from 0 to about 3 mole percent, an alkalimetal oxide selected from the group consisting of K 0 and Na O in amountfrom about 10 to about 15 mole percent, and MgO in amount from O toabout 5 mole percent, the sum of the A1 0 Zr0 and MgO being from about 3to about 10 mole percent.

3. The composition according to claim 2 in which said glaze furthercontains from about 1 to about 3 mole percent of P 0 4. The compositionaccording to claim 2 in which the said glaze further contains from about1 to about 5 mole I References Cited in the file of this patent UNITEDSTATES PATENTS Armistead Nov. 23, 1948 1,948,461 Kreidl Feb. 20, 19342,093,194 Geppert Sept. 14, 1937 2,688,560 Armistead Sept. 7, 19542,748,006 Kreidl et al. May 29, 1956 2,799,590 Armistead July 16, 1957

1. A FRIT COMPOSITION OF THE SELF-OPACIFYING ALKALI BOROALUMINOSILICATETYPE CONSISTING ESSENTIALLY OF SIO2 IN AMOUNT FROM ABOUT 55 TO ABOUT 70MOLE PERCENT, B2O3 IN AMOUNT FROM ABOUT 7 TO ABOUT 15 MOLE PERCENT,A12O3 IN AMOUNT FROM ABOUT 1 TO ABOUT 5 MOLE PERCENT, TIO2 IN AMOUNTFROM ABOUT 7 TO ABOUT 15 MOLE PERCENT, ZRO2 IN AMOUNT FROM 0 TO ABOUT 3MOLE PERCENT, AN ALKALI METAL OXIDE SELECTED FROM THE GROUP CONSITING OFK2O AND NA2O IN AMOUNT FROM ABOUT 10 TO ABOUT 15 MOLE PERCENT, AND MGOIN AMOUNT FROM 0 TO ABOUT 5 MOLE PERCENT, THE SUM OF THE AL2O3, ZRO2 ANDMGO BEING FROM ABOUT 3 TO ABOUT 10 MOLE PERCENT.